arXiv subjects

Zuman Zhang

Publications and source records attributed to Zuman Zhang.

12 recordsLinked to original sources

arXiv2026

A comparative study of $T_{cc}$ versus $X(3872)$ production in $pp$ collisions at $\sqrt{s}=$ 7 TeV

The production of exotic hadrons $T_{cc}$ and $X(3872)$ in $pp$ collisions at $\sqrt{s}=7$ TeV is compared using the parton and hadron cascade model PACIAE together with the dynamically constrained phase-space coalescence model DCPC. In the simulation, the compact tetraquark state and the loose molecular state are formed in the partonic and hadronic levels, respectively. Our analysis of the transverse momentum spectra reveals a significant discrepancy between the compact state and the molecular states. Furthermore, the production asymmetry between $T_{cc}^+$ and $T_{cc}^-$ is investigated. Finally, the coalescence parameters are extracted from the calculated spectra to further characterize the emission source properties. These distributions are proposed as valuable criteria for distinguishing between these states and investigating their internal structures in experimental measurements.

hep-ph↗

arXiv2025

Perturbative and nonperturbative properties of heavy quark transport in a thermal SU(3) gluon plasma

We investigate the perturbative and nonperturbative aspects of heavy quark transport in a thermal SU(3) gluon plasma. Based on the soft-hard factorized model, we extend the original perturbative framework to the near-critical temperature region, where nonperturbative effects become significant. The transition behavior of the semi-quark-gluon-plasma (semi-QGP) is described via a temperature-dependent background field incorporated in the background field effective theory. By implementing this approach, we quantitatively evaluate the collisional energy loss and momentum diffusion coefficients of charm and bottom quarks as functions of the incoming energy and medium temperature. Our results show a distinct suppression of both the energy loss and the diffusion coefficients relative to conventional perturbative estimates, especially near the critical temperature. This suppression originates from the emergence of a temperature-dependent color background field, which effectively reduces the color charge screening of the medium. These findings provide important theoretical insight into the phenomenology of heavy-flavor probes, offering a unified theoretical framework applicable across both high- and low-momentum regimes.

hep-ph↗

arXiv2025

Soft-hard factorization of heavy-quark transport in QCD matter at finite chemical potential

We calculate the collisional energy loss and momentum diffusion coefficients of heavy quarks traversing a hot and dense QCD medium at finite quark chemical potential, $\mu\neq0$. The analysis is performed within an extended soft-hard factorization model (SHFM) that consistently incorporates the $\mu$-dependence of the Debye screening mass $M_D(\mu)$ and of the fermionic thermal distribution functions. Both the energy loss and the diffusion coefficients are found to increase with $\mu$, with the enhancement being most pronounced at low temperatures where the chemical potential effects dominate the medium response. To elucidate the origin of this dependence, we derive analytic high-energy approximations in which the leading $\mu$-corrections appear as logarithmic terms: a soft logarithm $\sim\mu^{2}\ln(|t^{*}|/M_{D}^{2})$ from $t$-channel scattering off thermal gluonic excitations, and a hard logarithm $\sim\mu^{2}\ln(E_{1}T/|t^{*}|)$ from scattering off thermal quarks. In the complete result the dependence on the intermediate separation scale $t^{\ast}$ cancels, as required. We also confirm the expected mass hierarchy $-dE/dz(charm)<-dE/dz(bottom)$ at fixed velocity. Our findings demonstrate that finite chemical potential plays a significant role in heavy-quark transport and must be included in theoretical descriptions of heavy-flavor dynamics in baryon-rich environments, such as those probed in the RHIC Beam Energy Scan, and at FAIR and NICA.

hep-ph↗

arXiv2025

Investigating the transverse-momentum- and pseudorapidity-dependent flow vector decorrelation in p--Pb collisions with a Multi-Phase Transport model

The event-by-event fluctuations in the initial energy density of the nuclear collisions lead to the decorrelation of second order flow vector, as known as its transverse-momentum ($p_{\mathrm{T}}$) and pseudorapidity ($\eta$) dependence as observed in high-energy heavy-ion collisions. Existing measurements at the CERN Large Hadron Collider shown that these decorrelations are also observed in small collision systems. In this work, a systematic study of the transverse-momentum- and pseudorapidity-dependent flow vector decorrelation is performed in p--Pb collisions at the 5.02 TeV with A Multi-Phase Transport (AMPT) model using different tunings of the initial conditions, partonic and hadronic interactions. It is found that the string-melting version of the AMPT model provides a reasonable description of the measured flow vector decorrelation as a function of $p_{\mathrm{T}}$ and $\eta$. We demonstrate that the hadronic scatterings do not have significant impact on decorrelation in p--Pb collisions for different centrality selections, while both initial conditions and partonic interactions influence the magnitude of the decorrelations. In addition, we found that the subtraction of the nonflow, especially the long-range jet correlation, is crucial for the accurate extraction of the flow vector decorrelation in small collision systems. The comparison of data and model presented in this paper provide further insights in understanding the fluctuations of the flow vector with $p_{\mathrm{T}}$ and $\eta$ in small collision systems and has referential value for future measurements.

hep-ph↗

arXiv2025

Study of QCD critical point with three-nucleon correlations in light nuclei yields ratios using PYTHIA8/Angantyr

This study utilizes the PYTHIA8 Angantyr model to systematically investigate the effects of three nucleons correlation $C_{n^2p}$ on the light nuclei yield ratio $N_tN_p/N_d^2$ in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The analysis explores this property across different rapidity ranges, collision centralities, and collision energies, while also examining the roles of multi-parton interactions (MPI) and color reconnection (CR) mechanisms. The results show that the light nuclei yield ratio remains stable with changes in rapidity coverage and collision centrality but slightly increases with rising collision energy. The impact of CR on the light nuclei yield ratio depends entirely on the presence of MPI; when MPI is turned off, CR has no effect. Additionally, the three-nucleon correlation, enhances the light nuclei yield ratio in both central and peripheral collisions. However, the non-monotonic energy dependence observed in experiments, the peak at $\sqrt{s_{\rm NN}}$ = $20\sim30$ GeV reported by the STAR experiment, cannot be explained by the Angantyr model due to its lack of key mechanisms related to the quark-gluon plasma (QGP). Nevertheless, the Angantyr model serves as an important baseline for studying collision behaviors in the absence of QGP effects.

nucl-th↗

arXiv2025

Study the structure of X(3872) from its lineshape

We fit the invariant mass distribution of ${X(3872)}\rightarrow{J}/ψπ^+π^-$ from LHCb using the propagator for S-wave near-threshold states in effective field theory. In this way, we can directly determine the $Z$ which measures the projection of the bound state on the compact state in ${X(3872)}$. Consequently, the structure of ${X(3872)}$ can be elucidated. Moreover, the fitting result also can describe well the data for ${X(3872)}\rightarrow{D}^{0}\overline{D}^{0*}$ from Belle experiment, which demonstrate the reliability of our fitting. The fitting indicates that $Z$ is a non-vanishing value within error, which supports that $X(3872)$ has a compact short-distant core.

hep-ph↗

arXiv2025

Three-Nucleon Correlations in Light Nuclei Yields Ratios from AMPT Model for QCD Critical Point Investigation

This research use the AMPT model in Au+Au collisions to study the influence of the three nucleons correlation $C_{n^2p}$ on the light nuclei yield ratios. It is found that neglecting $C_{n^2p}$ leads to an overestimated relative neutron density fluctuation extraction. Including $C_{n^2p}$ will enhances the agreement with experimental results with higher yield ratios, yet it does not change the energy dependence of the yield ratio. Since there is no first-order phase transition or critical physics in the AMPT model, our work fails to reproduce the experimental energy-dependent peak around $\sqrt{s_\text{NN}} = $20-30 GeV. Our work might offer a baseline for investigating critical physics phenomena using the light nuclei production as a probe.

nucl-th↗

arXiv2025

Effect of Light Nuclei on Chemical Freeze-out Parameters at RHIC Energies

In this study, the chemical freeze-out of hadrons, including light-and strange-flavor particles and light nuclei, produced in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC), was investigated. Using the thermal-FIST thermodynamic statistical model, we analyzed various particle sets: those inclusive of light nuclei, those exclusive to light nuclei, and those solely comprising light nuclei. We determined the chemical freeze-out parameters at $\sqrt{s_\text{NN}}=$ 7.7--200 GeV and four different centralities. A significant finding was the decrease in the chemical freeze-out temperature $T_{\textrm{ch}}$ with light nuclei inclusion, with an even more pronounced reduction when considering light nuclei yields exclusively. This suggests that light nuclei formation occurs at a later stage in the system's evolution at RHIC energies. We present parameterized formulas that describe the energy dependence of $T_{\textrm{ch}}$ and the baryon chemical potential $μ_B$ for three distinct particle sets in central Au+Au collisions at RHIC energies. Our results reveal at least three distinct $T_{\textrm{ch}}$ at RHIC energies correspond to different freeze-out hypersurfaces: a light-flavor freeze-out temperature of $T_L$ = 150.2$\pm$6 MeV, a strange-flavor freeze-out temperature $T_s$ = 165.1$\pm$2.7 MeV, and a light-nuclei freeze-out temperature $T_{\textrm{ln}}$ = 141.7$\pm$1.4 MeV. Notably, at the Large Hadron Collider (LHC) Pb+Pb 2.76 TeV, the expected lower freeze-out temperature for light nuclei was not observed; instead, the $T_{\textrm{ch}}$ for light nuclei was found to be approximately 10 MeV higher than that for light-flavor hadrons.

nucl-th↗

arXiv2024

The general propagator for S-wave threshold states

We demonstrate that the propagator, derived from an Effective Field Theory (EFT) that incorporates Weinberger's compositeness theorem, provides a more general formula for describing S-wave near-threshold states. By fitting the lineshape using this propagator, we can extract the $Z$ factor for these states and elucidate their structures.

hep-ph↗

arXiv2023

Investigating nonflow contribution subtraction in d-Au collisions with AMPT model

This paper presents research that focuses on nonflow contribution subtraction in heavy-ion collisions, using a multiphase transport model (AMPT). Specifically, the study aims to investigate the behavior of charged particle elliptic flow ($v_{\rm 2}$) in d-Au collisions at a collision energy of $\sqrt{s_{\rm NN}} = 200$ GeV and to determine the impact of nonflow sources, such as jet correlations and resonance decays, in small collision systems. To reduce nonflow effects, the per-trigger yield distribution in peripheral d-Au collisions or pp collisions with the same collision energy is subtracted. Our results show that the nonflow effects in central and mid-central collisions are not strongly dependent on subtracting the per-trigger yield distribution in peripheral d-Au collisions or pp collisions. Furthermore, the elliptic flow of charged particles, after removing nonflow effects through two subtracting methods from this work, exhibits consistency in various collision centrality classes. We also discuss comparisons with measurements from d-Au collisions at $\sqrt{s_{\rm NN}} = 200$ GeV. Overall, this work provides valuable insights and serves as a reference for researchers studying nonflow contribution subtraction in experiments with small collision systems.

nucl-ex↗

arXiv2022

Neutron density fluctuation and neutron-proton correlation from AMPT model

Using the multiphase transport (AMPT) model, we study the relative neutron density fluctuation and neutron-proton correlation in matter produced by Au+Au collisions at $\sqrt{s_\text{NN}} = $7.7-200 GeV. The rapidity, centrality, and energy dependence of these two observations are also discussed. The light nuclei yield ratio of proton, deuteron, and triton $N_tN_p/N_d^2$ calculated directly from the relative neutron density fluctuation and neutron-proton correlation, decreases with rapidity coverage and increases with collision centrality. Our study also found that the ratio does not exhibit any non-monotonic behavior in collision energy dependence. Since there is no first-order phase transition or critical physics in the AMPT model, our work provides a reference for extracting the relative neutron density fluctuation from light nuclei production in experiments.

nucl-th↗

arXiv2017

Production of muons from heavy-flavour hadron decays at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02~{\rm TeV}$}

The measurement of the production of single muons from heavy-flavour hadron decays at forward rapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02~{\rm TeV}$ collected in 2015 is presented as a function of transverse momentum ($p_{\rm T}$) and collision centrality. A strong suppression of the yield is observed at high $p_{\rm T}$ in the most central collisions compared to the binary-scaled expectation from pp collisions at the same energy. The $p_{\rm T}$-integrated nuclear modification factor ($R_{\rm AA}$) as function of the number of participating nucleons indicates an increase of the suppression from peripheral to central collisions. Comparisons with the results for Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76~{\rm TeV}$ and with transport model predictions are shown. A similar suppression is measured at both $\sqrt{s_{\rm NN}} = 2.76~{\rm TeV}$ and 5.02 TeV. The results available from $p_{\rm T} =$7 GeV/$c$ up to $p_{\rm T} =~$20 GeV/$c$, will provide new constraints on transport model ingredients and new insights on the understanding of the evolution of the hot and dense matter formed in ultra-relativistic heavy-ion collisions.

hep-ex↗